draft-ietf-idr-bgp-open-policy-00.txt   draft-ietf-idr-bgp-open-policy-01.txt 
Network Working Group A. Azimov Network Working Group A. Azimov
Internet-Draft E. Bogomazov Internet-Draft E. Bogomazov
Intended status: Standards Track Qrator Labs Intended status: Standards Track Qrator Labs
Expires: December 20, 2017 R. Bush Expires: January 4, 2018 R. Bush
Internet Initiative Japan Internet Initiative Japan
K. Patel K. Patel
Arrcus, Inc. Arrcus, Inc.
K. Sriram K. Sriram
US NIST US NIST
June 18, 2017 July 3, 2017
Route Leak Prevention using Roles in Update and Open messages Route Leak Prevention using Roles in Update and Open messages
draft-ietf-idr-bgp-open-policy-00 draft-ietf-idr-bgp-open-policy-01
Abstract Abstract
Route Leaks are the propagation of BGP prefixes which violate Route Leaks are the propagation of BGP prefixes which violate
assumptions of BGP topology relationships; e.g. passing a route assumptions of BGP topology relationships; e.g. passing a route
learned from one peer to another peer or to a transit provider, learned from one peer to another peer or to a transit provider,
passing a route learned from one transit provider to another transit passing a route learned from one transit provider to another transit
provider or to a peer. Today, approaches to leak prevention rely on provider or to a peer. Today, approaches to leak prevention rely on
marking routes according to operator configuration options without marking routes according to operator configuration options without
any check that the configuration corresponds to that of the BGP any check that the configuration corresponds to that of the BGP
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 20, 2017. This Internet-Draft will expire on January 4, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Peering Relationships . . . . . . . . . . . . . . . . . . 3 1.1. Peering Relationships . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Role Definitions . . . . . . . . . . . . . . . . . . . . . . 3 3. Role Definitions . . . . . . . . . . . . . . . . . . . . . . 3
4. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Role capability . . . . . . . . . . . . . . . . . . . . . . . 5 5. Role capability . . . . . . . . . . . . . . . . . . . . . . . 4
6. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5 6. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 5
7. Restrictions on the Complex role . . . . . . . . . . . . . . 6 7. BGP Internal Only To Customer attribute . . . . . . . . . . . 6
8. BGP Internal Only To Customer attribute . . . . . . . . . . . 6 8. Attribute or Community . . . . . . . . . . . . . . . . . . . 6
9. Compatibility with BGPsec . . . . . . . . . . . . . . . . . . 7 9. Compatibility with BGPsec . . . . . . . . . . . . . . . . . . 7
10. Additional Considerations . . . . . . . . . . . . . . . . . . 7 10. Additional Considerations . . . . . . . . . . . . . . . . . . 7
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
12. Security Considerations . . . . . . . . . . . . . . . . . . . 8 12. Security Considerations . . . . . . . . . . . . . . . . . . . 8
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
14.1. Normative References . . . . . . . . . . . . . . . . . . 8 14.1. Normative References . . . . . . . . . . . . . . . . . . 8
14.2. Informative References . . . . . . . . . . . . . . . . . 9 14.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Preamble 1. Preamble
1.1. Peering Relationships 1.1. Peering Relationships
Despite uses of words such as "Customer," "Peer." etc. the intent is Despite uses of words such as "Customer," "Peer." etc. the intent is
not business relationships, who pays whom, etc. These are common not business relationships, who pays whom, etc. These are common
terms to represent restrictions on BGP propagation, some times known terms to represent restrictions on BGP route propagation, sometimes
as Gao/Rexford. E.g. if A is a "peer" of B and C, A does not known as Gao-Rexford model. E.g. if A is a "peer" of B and C, A does
propagate B's prefixes to C. If D is a "customer" of E and F, D does not propagate B's prefixes to C. If D is a "customer" of E and F, D
not propagate prefixes learned from E to F. does not propagate prefixes learned from E to F.
As the whole point of route leak detection and prevention is to As the whole point of route leak detection and prevention is to
prevent vioation of these relationships, they are inescapable. prevent vioation of these relationships, they are inescapable.
2. Introduction 2. Introduction
This document specifies a new BGP Capability Code, [RFC5492] Sec 4, This document specifies a new BGP Capability Code, [RFC5492] Sec 4,
which two BGP speakers MAY use to ensure that they MUST agree on which two BGP speakers MAY use to ensure that they MUST agree on
their relationship; i.e. customer and provider or peers. Either or their relationship; i.e. customer and provider or peers. Either or
both may optionally be configured to require that this option be both may optionally be configured to require that this option be
exchanged for the BGP Open to succeed. exchanged for the BGP Open to succeed.
Also this document specifies a way to mark routes according to BGP Also this document specifies a way to mark routes according to BGP
Roles established in OPEN and a way to create double-boundary filters Roles established in OPEN message and a way to create double-boundary
for prevention of route leaks via new BGP Path Attribute. filters for prevention of route leaks via new BGP Path Attribute.
For the purpose of this document, BGP route leaks are when a BGP For the purpose of this document, BGP route leaks are when a BGP
route was learned from transit provider or peer and is announced to route was learned from transit provider or peer and is announced to
another provider or peer. See another provider or peer. See
[I-D.ietf-grow-route-leak-problem-definition]. These are usually the [I-D.ietf-grow-route-leak-problem-definition]. These are usually the
result of misconfigured or absent BGP route filtering or lack of result of misconfigured or absent BGP route filtering or lack of
coordination between two BGP speakers. coordination between two BGP speakers.
[I-D.ietf-idr-route-leak-detection-mitigation] The mechanism proposed [I-D.ietf-idr-route-leak-detection-mitigation] The mechanism proposed
in that draft provides the opportunity to detect route leaks made by in that draft provides the opportunity to detect route leaks made by
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A Customer: accepts 'transit routes' from its provider(s) and A Customer: accepts 'transit routes' from its provider(s) and
announces their own routes and the routes they have learned from announces their own routes and the routes they have learned from
the transitive closure of their customers (AKA their 'customer the transitive closure of their customers (AKA their 'customer
cone') to their provider(s). cone') to their provider(s).
A Peer: announces their routes and the routes from their customer A Peer: announces their routes and the routes from their customer
cone to other Peers. cone to other Peers.
An Internal: announces all routes, accepts all routes. An Internal: announces all routes, accepts all routes.
A Complex: BGP relationship is an attempt to allow those whose
policy may vary by prefix. It is aptly named and the authors
question its real utility.
Of course, any BGP speaker may apply policy to reduce what is Of course, any BGP speaker may apply policy to reduce what is
announced, and a recipient may apply policy to reduce the set of announced, and a recipient may apply policy to reduce the set of
routes they accept. routes they accept.
4. BGP Role 4. BGP Role
BGP Role is new mandatory configuration option. It reflects the BGP Role is new configuration option that SHOULD be configured at
real-world agreement between two BGP speakers about their peering each BGP session. It reflects the real-world agreement between two
relationship. BGP speakers about their peering relationship.
Allowed Role values are: Allowed Role values for eBGP sessions are:
o Provider - sender is a transit provider to neighbor; o Provider - sender is a transit provider to neighbor;
o Customer - sender is customer of neighbor; o Customer - sender is customer of neighbor;
o Peer - sender and neighbor are peers; o Peer - sender and neighbor are peers;
o Internal - sender and neighbor is part of same organization. This o Internal - sender and neighbor is part of same organization.
includes but is not limited to situation when sender and neighbor
are in same AS.
o Complex - sender has a non-standard relationship and wants to use For iBGP sessions only Internal role MAY be configured.
manual per-prefix based role policies.
Since BGP Role reflects the relationship between two BGP speakers, it Since BGP Role reflects the relationship between two BGP speakers, it
could also be used for more than route leak mitigation. could also be used for more than route leak mitigation.
5. Role capability 5. Role capability
The TLV (type, length, value) of the BGP Role capability are: The TLV (type, length, value) of the BGP Role capability are:
o Type - <TBD1>; o Type - <TBD1>;
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o Value - integer corresponding to speaker' BGP Role. o Value - integer corresponding to speaker' BGP Role.
+--------+----------------------+ +--------+----------------------+
| Value | Role name | | Value | Role name |
+--------+----------------------+ +--------+----------------------+
| 0 | Undefined | | 0 | Undefined |
| 1 | Sender is Peer | | 1 | Sender is Peer |
| 2 | Sender is Provider | | 2 | Sender is Provider |
| 3 | Sender is Customer | | 3 | Sender is Customer |
| 4 | Sender is Internal | | 4 | Sender is Internal |
| 5 | Sender is Complex |
+--------+----------------------+ +--------+----------------------+
Table 1: Predefined BGP Role Values Table 1: Predefined BGP Role Values
6. Role correctness 6. Role correctness
Section 4 described how BGP Role is a reflection of the relationship Section 4 described how BGP Role is a reflection of the relationship
between two BGP speakers. But the mere presence of BGP Role doesn't between two BGP speakers. But the mere presence of BGP Role doesn't
automatically guarantee role agreement between two BGP peers. automatically guarantee role agreement between two BGP peers.
To enforce correctness, the BGP Role check is used with a set of To enforce correctness, the BGP Role check is used with a set of
constrains on how speakers' BGP Roles MUST corresponded. Of course, constrains on how speakers' BGP Roles MUST corresponded. Of course,
each speaker MUST announce and accept the BGP Role capability in the each speaker MUST announce and accept the BGP Role capability in the
BGP OPEN message exchange. BGP OPEN message exchange.
If a speaker receives a BGP Role capability, it SHOULD check value of If a speaker receives a BGP Role capability, it MUST check value of
the received capability with its own BGP Role. The allowed pairings the received capability with its own BGP Role (if it is set). The
are (first a sender's Role, second the receiver's Role): allowed pairings are (first a sender's Role, second the receiver's
Role):
+--------------+----------------+ +--------------+----------------+
| Sender Role | Receiver Role | | Sender Role | Receiver Role |
+--------------+----------------+ +--------------+----------------+
| Peer | Peer | | Peer | Peer |
| Provider | Customer | | Provider | Customer |
| Customer | Provider | | Customer | Provider |
| Internal | Internal | | Internal | Internal |
| Complex | Complex |
+--------------+----------------+ +--------------+----------------+
Table 2: Allowed Role Capabilities Table 2: Allowed Role Capabilities
In all other cases speaker MUST send a Role Mismatch Notification In all other cases speaker MUST send a Role Mismatch Notification
(code 2, sub-code <TBD2>). (code 2, sub-code <TBD2>).
6.1. Strict mode 6.1. Strict mode
A new BGP configuration option "strict mode" is defined with values A new BGP configuration option "strict mode" is defined with values
of true or false. If set to true, then the speaker MUST refuse to of true or false. If set to true, then the speaker MUST refuse to
establish a BGP session with peers which do not announce the BGP Role establish a BGP session with peers which do not announce the BGP Role
capability in their OPEN message. If a speaker rejects a connection, capability in their OPEN message. If a speaker rejects a connection,
it MUST send a Connection Rejected Notification [RFC4486] it MUST send a Connection Rejected Notification [RFC4486]
(Notification with error code 6, subcode 5). By default strict mode (Notification with error code 6, subcode 5). By default strict mode
SHOULD be set to false for backward compatibility with BGP speakers, SHOULD be set to false for backward compatibility with BGP speakers,
that do not yet support this mechanism. that do not yet support this mechanism.
7. Restrictions on the Complex role 7. BGP Internal Only To Customer attribute
The Complex role should be set only if the relationship between BGP
neighbors can not be described using simple Customer/Provider/Peer
roles. For a example, if neighbor is literal peer, but for some
prefixes it provides full transit; the complex role SHOULD be set on
both sides. In this case roles Customer/Provider/Peer should be set
on per-prefix basis, keeping the abstraction from filtering
mechanisms (Section 8).
If role is not Complex all per-prefix role settings MUST be ignored.
8. BGP Internal Only To Customer attribute
The Internal Only To Customer (iOTC) attribute is a new optional, The Internal Only To Customer (iOTC) attribute is a new optional,
non-transitive BGP Path attribute with the Type Code <TBD3>. This non-transitive BGP Path attribute with the Type Code <TBD3>. This
attribute has zero length as it is used only as a flag. attribute has zero length as it is used only as a flag.
There are four rules for setting the iOTC attribute: There are three rules of iOTC attribute usage:
1. The iOTC attribute MUST be added to all incoming routes if the 1. The iOTC attribute MUST be added to all incoming routes if the
receiver's Role is Customer or Peer; receiver's Role is Customer or Peer;
2. The iOTC attribute MUST be added to all incoming routes if the 2. Routes with the iOTC attribute set MUST NOT be announced by a
receiver's Role is Complex and the prefix Role is Customer or
Peer;
3. Routes with the iOTC attribute set MUST NOT be announced by a
sender whose Role is Customer or Peer; sender whose Role is Customer or Peer;
4. Routes with the iOTC attribute set MUST NOT be announced if by a 3. A sender MUST NOT include this attribute in UPDATE messages if
sender whose Role is Complex and the prefix Role is Customer or its Role is Customer, Provider or Peer. If it is contained in an
Peer; UPDATE message from eBGP speaker and receiver's Role is Customer,
Provider, Peer or unspecified, then this attribute MUST be
removed.
These four rules provide mechanism that strongly prevents route leak These three rules provide mechanism that strongly prevents route leak
creation by an AS. creation by an AS.
8. Attribute or Community
Having the relationship hard set by agreement between the two peers
in BGP OPEN is critical; the routers enforce the relationship
irrespective of operator configuration errors.
Similarly, it is critical that the application of that relationship
on prefix propagation using iOTC is enforced by the router(s), and
minimally exposed to user misconfiguration. There is a question
whether the iOTC marking should be an attribute or a well-known
community.
There is a long and sordid history of mis-configurations inserting
incorrect communities, deleting communities, ignoring well-known
community markings etc. In this mechanism's case, an operator could,
for example, accidentally strip the well-known community on receipt.
As opposed to communities, BGP attributes may not be generally
modified or filtered by the operator. The router(s) enforce them.
This is the desired property for the iOTC marking. Hence, this
document specifies iOTC as an attribute.
9. Compatibility with BGPsec 9. Compatibility with BGPsec
As the iOTC field is non-transitive, it is not seen by or signed by As the iOTC field is non-transitive, it is not seen by or signed by
BGPsec [I-D.ietf-sidr-bgpsec-protocol]. BGPsec [I-D.ietf-sidr-bgpsec-protocol].
10. Additional Considerations 10. Additional Considerations
As the BGP Role reflects the relationship between neighbors, it can As the BGP Role reflects the relationship between neighbors, it can
also have other uses. As an example, BGP Role might affect route also have other uses. As an example, BGP Role might affect route
priority, or be used to distinguish borders of a network if a network priority, or be used to distinguish borders of a network if a network
consists of multiple AS. consists of multiple AS.
Though such uses may be worthwhile, they are not the goal of this Though such uses may be worthwhile, they are not the goal of this
document. Note that such uses would require local policy control. document. Note that such uses would require local policy control.
As BGP role configuration results in automatic creation of inbound/
outbound filters, existence of roles should be treated as existence
of Import and Export policy. [I-D.ietf-grow-bgp-reject]
This document doesn't provide any security measures to check This document doesn't provide any security measures to check
correctness of per-prefix roles, so the Complex role should be used correctness of iOTC usage if role isn't configured.
with great caution. It is as dangerous as current BGP peering.
11. IANA Considerations 11. IANA Considerations
This document defines a new Capability Codes option [to be removed This document defines a new Capability Codes option [to be removed
upon publication: http://www.iana.org/assignments/capability-codes/ upon publication: http://www.iana.org/assignments/capability-codes/
capability-codes.xhtml] [RFC5492], named "BGP Role", assigned value capability-codes.xhtml] [RFC5492], named "BGP Role", assigned value
<TBD1> . The length of this capability is 1. <TBD1> . The length of this capability is 1.
The BGP Role capability includes a Value field, for which IANA is The BGP Role capability includes a Value field, for which IANA is
requested to create and maintain a new sub-registry called "BGP Role requested to create and maintain a new sub-registry called "BGP Role
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are the result of BGP policy misconfiguration. are the result of BGP policy misconfiguration.
Deliberate sending of a known conflicting BGP Role could be used to Deliberate sending of a known conflicting BGP Role could be used to
sabotage a BGP connection. This is easily detectable. sabotage a BGP connection. This is easily detectable.
BGP Role is disclosed only to an immediate BGP neighbor, so it will BGP Role is disclosed only to an immediate BGP neighbor, so it will
not itself reveal any sensitive information to third parties. not itself reveal any sensitive information to third parties.
13. Acknowledgments 13. Acknowledgments
The authors wish to thank Douglas Montgomery, Brian Dickson, and The authors wish to thank Douglas Montgomery, Brian Dickson, Andrei
Andrei Robachevsky for their contributions to a variant of this work. Robachevsky and Daniel Ginsburg for their contributions to a variant
of this work.
14. References 14. References
14.1. Normative References 14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 9, line 11 skipping to change at page 8, line 48
[RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease
Notification Message", RFC 4486, DOI 10.17487/RFC4486, Notification Message", RFC 4486, DOI 10.17487/RFC4486,
April 2006, <http://www.rfc-editor.org/info/rfc4486>. April 2006, <http://www.rfc-editor.org/info/rfc4486>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <http://www.rfc-editor.org/info/rfc5492>. 2009, <http://www.rfc-editor.org/info/rfc5492>.
14.2. Informative References 14.2. Informative References
[I-D.ietf-grow-bgp-reject]
Mauch, J., Snijders, J., and G. Hankins, "Default EBGP
Route Propagation Behavior Without Policies", draft-ietf-
grow-bgp-reject-08 (work in progress), May 2017.
[I-D.ietf-grow-route-leak-problem-definition] [I-D.ietf-grow-route-leak-problem-definition]
Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., Sriram, K., Montgomery, D., McPherson, D., Osterweil, E.,
and B. Dickson, "Problem Definition and Classification of and B. Dickson, "Problem Definition and Classification of
BGP Route Leaks", draft-ietf-grow-route-leak-problem- BGP Route Leaks", draft-ietf-grow-route-leak-problem-
definition-06 (work in progress), May 2016. definition-06 (work in progress), May 2016.
[I-D.ietf-idr-route-leak-detection-mitigation] [I-D.ietf-idr-route-leak-detection-mitigation]
Sriram, K., Montgomery, D., Dickson, B., Patel, K., and A. Sriram, K., Montgomery, D., Dickson, B., Patel, K., and A.
Robachevsky, "Methods for Detection and Mitigation of BGP Robachevsky, "Methods for Detection and Mitigation of BGP
Route Leaks", draft-ietf-idr-route-leak-detection- Route Leaks", draft-ietf-idr-route-leak-detection-
mitigation-03 (work in progress), May 2016. mitigation-03 (work in progress), May 2016.
[I-D.ietf-sidr-bgpsec-protocol] [I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M. and K. Sriram, "BGPsec Protocol Lepinski, M. and K. Sriram, "BGPsec Protocol
Specification", draft-ietf-sidr-bgpsec-protocol-15 (work Specification", draft-ietf-sidr-bgpsec-protocol-15 (work
in progress), March 2016. in progress), March 2016.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
Authors' Addresses Authors' Addresses
Alexander Azimov Alexander Azimov
Qrator Labs Qrator Labs
Email: aa@qrator.net Email: aa@qrator.net
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